Method and device for the production of a one-layered or multilayered nonwoven fabric

ABSTRACT

The invention relates to a method for the production of a one-layered or multilayered nonwoven fabric, a machine for the production of such a nonwoven fabric, and a correspondingly produced nonwoven fabric. The task of improving such a method and a production apparatus underlies the invention to the effect that projecting loops and fibrils no longer stick out, and thus individual filaments can be prevented from pulling out during the use of the nonwoven fabric. According to the invention, this is achieved in that the nonwoven fabric is smoothed after water needling by the use of a calendar. The machine according to the invention is characterized by the fact that the machine has a spun bonded fabric, at least one subsequent needling device, a dryer connected thereto, and thereafter at least one calendar.

The invention relates to a method for producing a one-layered ormultilayered nonwoven fabric, as disclosed in the preamble to claim 1,as well as the apparatus for producing such a nonwoven fabric and also acorrespondingly produced nonwoven fabric.

A nonwoven fabric composed of a plurality of yarn-type fiber groups isalready known (EP 0 626 902 B1), wherein these groups are joined atconnecting points through fibers belonging to a plurality of thesegroups to delimit a predetermined pattern of holes in the nonwovenfabric, wherein the nonwoven fabric has a transparency index of at least0.5 and a computed fiber bundle density of at least 0.14 gram per cubiccentimeter.

It is the object of the present invention to improve a production methodand a production apparatus in accordance with the respective preamble.The goal advantageously is to prevent loops or fibrils from sticking outof the nonwoven fabric, thereby preventing the pulling out of individualfilaments during the use of the nonwoven fabric.

This object is solved according to the invention by smoothing thenonwoven fabric with the aid of a calender, following the water needlingprocess. The nonwoven fabric preferably is a spun-bonded fabric that issubjected to a hydrodynamic needling technique, is subsequently dried,and is then smoothed with the aid of a calender.

As a result, the loops or fibrils that stick out and are extremelybothersome when using a one-layer or also a multilayer nonwoven fabricare welded-on in an easy operation by the calender and aresimultaneously smoothed, so as to avoid the pilling effect or the nap orlint forming.

The apparatus advantageously includes a spun-bonding plant by means ofwhich the filaments are deposited onto an endless belt that is embodiedas a screen belt, as well as at least one downstream-connected needlingdevice, an adjoining dryer, and at least one calender following thedryer.

According to a modification of the invention, the apparatus canoptionally comprise a spun-bonding plant, a downstream-connectedpre-needling device that can be admitted with low water pressure, anadjoining second needling device with thereto assigned at least onestructuring drum with a suction box, as well as an adjoining dryer andat least one calender that follows the dryer.

It is furthermore advantageous if the apparatus includes a spun-bondingplant with downstream-connected pre-needling device that can be admittedwith low water pressure, a following second needling device with atleast one structuring drum, an adjoining dryer, and at least onecalender following the dryer.

The apparatus is advantageously also provided with a spun-bonding plant,by means of which the filaments are deposited on the structuring drum,as well as the needling device that is directly assigned to thestructuring drum, the adjoining dryer and at least the calenderfollowing the dryer.

Finally, according to a preferred embodiment of the inventive solution,the apparatus comprises the spun-bonding plant with downstream-connectedpre-needling device that can be admitted with low water pressure, theadjoining second needling device that is provided with at least onestructured drum, and a calender following the second needling device.

Of particular importance to the present invention is that at least oneconveying drum is assigned to the structured drum, such that the endlessbelt is guided S-shaped or in the form of two semi-circles across thestructured drum and the conveying drum. The different systems describedin the above can be used to achieve a cost-effective production of anoptimum nonwoven fabric for extreme use, which does not pillar.

In connection with the embodiment and arrangement according to theinvention, the endless belt can advantageously be embodied as a conveyorbelt or as a structured belt.

The invention relates to one-layer or multilayer nonwoven fabrics whichare additionally and advantageously perforated by using one of the waterneedling processes. Nonwoven fabrics having a weight per unit area of7-300 g/m² are preferably processed. The processing speed is at least100 m/min while the fiber strength—filament strength—preferably rangesfrom 0.4 to 10 dtex.

Additional advantages and details of the invention are explained in thepatent claims and in the description and are illustrated in the Figures,which show in:

FIG. 1 A schematic representation of a spun-bonding plant with adownstream-arranged rotating belt on which the filaments are deposited,as well as a needling device, a dryer and a calender;

FIG. 2 A similar representation as shown in FIG. 1, for which theendless belt is guided S-shaped or in the form of two semi-circles overthe drums;

FIG. 3 A similar representation as shown in FIG. 1, but where theendless belt is replaced by a drum;

FIG. 4 A similar representation as shown in FIG. 1, for which theendless belt is embodied only as a conveying element;

FIG. 5 A segment of the endless belt or a segment of a structured drumon which the filaments are deposited;

FIG. 6 A nonwoven fabric with numerous openings, which is processed onthe endless belt.

The drawing shows a spun-bonding plant 1, which is used for depositingand further transporting endless filaments 4 on a continuously rotatingbelt 3 that is guided over four rollers 2, wherein at least one of thefour rollers 2 is embodied as a drive roller.

The endless belt 3 is shown in further detail in FIG. 5. This belt is ascreen belt composed of webs or wires 5, arranged spaced apart andextending at right angles to each other, between which small andapproximately rectangular openings 6 are formed that allow the water 8exiting from a needling device 7.1 to flow through these openings 6.Owing to the screen belt 3, the water is forced to travel longerdistances and the individual filaments are displaced to the side, asshown in FIG. 6, thereby causing corresponding openings 6.1 to form in anonwoven fabric 14, which openings match the shape of the openings 6 inthe endless belt 3.

Following the needling operation, the nonwoven fabric 14 moves through adryer 9, which can be embodied as infrared inline airflow dryer. Thenonwoven fabric 14 is then smoothed with the aid of a calender 10, sothat any filaments or loops or fibrils that still stick out are pushedback into the nonwoven fabric 14.

With the aid of the following calender 10, the projecting loops orfibrils are welded on and are simultaneously also pushed against thesurface of the nonwoven fabric 14.

The above-described operational process and treatment of the nonwovenfabric 14 are realized in a similar manner in all systems shown in FIGS.2 to 4.

According to the exemplary embodiment shown in FIG. 2, the nonwovenfabric 14 is supplied by the endless belt 3 to the water needling device7.1 with a suction box 7.3, so that at this location the nonwoven fabric14 can be roughly pre-compacted with low pressure. As a result, thenonwoven fabric 14 is compacted in such a way that it can subsequentlybe guided S-shaped or in the form of two semi-circles across two drums11 and 12, wherein the second drum 12 is assigned an additional needlingdevice 7.2 with a suction box 7.3. According to FIG. 4, the nonwovenfabric is taken over by the lower drum with the aid of suction pressure,is thus lifted off the screen belt with the aid of the drum 11 and issubsequently taken over by the drum 11 and, in the process, istransferred S-shaped to the drum 12 with thereto assigned suction box7.3. The nonwoven fabric 14 is thus pushed against the drum 12.

The first drum 11 is a conveying drum while the second drum 12 is astructured drum, which corresponds to the endless belt 3, shown in FIG.1, and is provided with numerous openings 6 corresponding to the screenbelt or endless belt 3 shown in FIG. 5. The endless belt according toFIG. 2 is not embodied as a perforated belt, but only as a conveyorbelt. The nonwoven fabric 14 is deposited on the conveyor belt 3, isthen transferred to the drum 11 and is held thereon with the aid of avacuum pressure. The perforation-creating openings provided in the drum12 are thus used to create the openings 6.1 shown in FIG. 6 in thenonwoven fabric 14, with the aid of the water needling device 7.1, 7.2.

For the exemplary embodiment according to FIG. 3, the endless beltsystem according to FIG. 1 is replaced by a structured drum 13 with theneedling device 7.1 and the suction box 7.3.

The exemplary embodiment shown in FIG. 4 does not comprise the dryer 9between the two deflection drums 11, 12 and the downstream connectedcalenders 10.

REFERENCE NUMBER LIST

-   1 spun-bonding plant-   2 roller-   3 endless belt, conveying belt, screen belt-   4 endless filament-   5 web, wire-   6 opening in the endless belt-   6.1 opening in the nonwoven fabric-   7.1 needling device-   7.2 needling device-   7.3 suction box-   8 water-   9 dryer-   10 calender-   11 conveying drum-   12 structured drum-   13 structured drum-   14 nonwoven fabric

1. A method for producing a one-layer or a multilayer nonwoven fabricwith a plurality of yarn-type fiber groups or endless filaments, whichare joined at least in the area of connecting locations, characterizedin that following the water needling, the nonwoven fabric is smoothedwith the aid of a calender.
 2. The method according to claim 1,characterized in that following the water needling, the nonwoven fabricis smoothed with the aid of a calender and that the calender is adjustedin such a way that more than 90% of the tensile strength of the nonwovenfabric is retained in conveying direction.
 3. The method according toclaim 1, characterized in that relative to the water needling, thenonwoven fabric is reduced in volume by 25% to 15%, or 22 to 18%, or byapproximately 20%.
 4. The method according to claim 1, characterized inthat the area subjected to pressure measures approximately 16% to 25%,or 17% to 22%, or 18% to 20% of the total surface area of the nonwovenfabric.
 5. The method according to claim 1, characterized in that thenonwoven fabric is treated with a smoothing roll temperature of between120° and 155°, or between 125° and 150°, or between 130° and 150°, orbetween 140° and 150° C.
 6. The method according to claim 1,characterized in that the nonwoven fabric is treated with an engravingtemperature between 120° and 155°, or between 125° and 150°, or between130° and 150°, or between 140° and 150° C.
 7. The method according toclaim 1, characterized in that the nonwoven fabric is treated with anengraving temperature that is approximately between 120° and 155°, orbetween 125° and 150°, or between 130° and 150°, or between 140° and150° C., and that a line pressure of between 20 and 30 or between 24 and28 N/mm is used during the subsequent calendering.
 8. The methodaccording to claim 1, characterized in that a drying operation takesplace between the water needling and the calendering.
 9. The methodaccording to claim 1, characterized in that the nonwoven fabric isperforated (openings 6.1) as a result of the water needling.
 10. Themethod according to claim 1, characterized in that a nonwoven fabricwith a weight per unit area of 7 to 300 g/m² is processed.
 11. Themethod according to claim 1, characterized in that the processing speedis at least 100 m/min.
 12. The method according to claim 1,characterized in that the nonwoven fabric has a fiber strength (diameterof the filaments) of between 0.4-10 dtex.
 13. An apparatus for realizingthe production method according to claim 1, characterized in that theapparatus comprises a spun-bonding plant, at least one downstreamconnected needling device and an adjoining dryer, which is followed byat least one calender.
 14. The apparatus according to claim 13,characterized in that the apparatus comprises a spun-bonding plant fordepositing the filaments on an endless belt, embodied as a screen belt,as well as at least one downstream connected needling device, anadjoining dryer, and at least one calender that follows the dryer. 15.The apparatus according to claim 13, characterized in that the apparatuscomprises the following: a spun-bonding plant; a down-stream arrangedpre-needling device that can be admitted with low water pressure; anadjoining second needling device with thereto assigned at least onestructured drum with a suction box; an adjoining dryer; and at least onecalender that follows the dryer.
 16. The apparatus according to claim13, characterized in that the apparatus comprises a spun-bonding plant,by means of which the filaments are deposited on a drum, as well as aneedling device that is directly assigned to the drum, the adjoiningdryer, and at least one calender that follows the dryer.
 17. Theapparatus according to claim 16, characterized in that the drum isembodied as a structured drum.
 18. The apparatus according to claim 1,characterized in that at least one conveying drum is assigned to thestructured drum, such that the endless belt is guided S-shaped or in theform of two semi-circles across the structured drum and the conveyingdrum.
 19. The apparatus according to claim 16, characterized in that theendless belt is embodied as a conveying belt or as a structured belt.20. A nonwoven fabric, characterized in that the nonwoven fabric isproduced in accordance to claim 1.